1. Field of the Invention
The present invention relates to a magnetic head used in a data writing/reading apparatus for writing data to or reading from a recording medium such as a magnetic disk or a magneto-optical disk. In this specification, a “magnetic head” is defined as any type of writing/reading head provided with a magnetic field generating coil. By this definition, a magneto-optical head may simply be referred to as “magnetic head.” The present invention also relates to a data writing/reading apparatus incorporating such a magnetic head.
2. Description of the Related Art
FIG. 7 shows a conventional magnetic head including a substrate 93 and a coil 92 formed on the substrate 93. The coil 92 is entirely enclosed by a transparent dielectric layer 94 that has a uniform thickness and covers entirely the upper surface of the substrate 93. Below the substrate 93 are provided a diametrically larger objective lens 91a and a diametrically smaller objective lens 91b. After being emitted from an unillustrated light source, laser beams are converged by the two objective lenses 91a, 91b and pass through the substrate 93 and the dielectric layer 94, to form a beam spot on the recording layer of the disk D. For performing data recording by magnetic field modulation, the magnetic field generated by the coil 92 is applied to the recording layer at the point where the beam spot is produced. For focus control, the magnetic head is supported by an actuator (not shown) so that it can be moved closer to or away from the disk D.
While the conventional magnetic head is advantageous in that the dielectric layer 94 of the uniform thickness protects the coil 92 from external mechanical damage, it has the following drawback.
Typically the magneto-optical disk D includes a thin substrate upon which a recording layer is formed. Due to this rather weak supporting structure, the disk D is liable to warp, thereby coming into contact with the edge 94a of the dielectric layer 94. Even if the disk D itself is not warped, it may tilt, as shown by the single-dot chain lines in FIG. 7, due to unsteady rotation of a spindle supporting the disk D. In this instance again, the disk D may come into contact with the edge 94a of the dielectric layer 94.
Unfavorably, the disk D may be damaged by the contact with the dielectric layer 94. Further, the actuator, which is coupled to the magnetic head, may also be damaged since a rather strong moment M can be exerted on the magnetic head when the disk D bumps into the dielectric layer 94.